1. Field of the Invention
The present invention relates to a control device for a window or windshield wiper apparatus with operating point-dependent wiping angle adaptation and to a method for operating this control device, and also to the wiper apparatus having the control device.
2. Description of the Related Art
A window wiper apparatus of a motor vehicle can be electronically controlled in order to optimize its operational behavior and properties. A certain set wiper arm course (set trajectory) is predetermined so that the wiper arm of the controlled window wiper apparatus has a desired course on the window of the motor vehicle. This predetermined wiper arm trajectory is usually stored in a control device of the window wiper apparatus. Various set wiper arm trajectories are provided, which are adapted to the several provided wiper speeds for the wiper arm. This adaptation is usually such that the turning point of the wiper arm at higher wiper speeds is reduced in comparison to the turning point at lower speeds.
High wiper speeds cause reduced friction moment between the wiper arm and the window, which itself causes increased wiper speeds of the wiper arm. Excessive oscillations of the wiper arm are compensated by the above-mentioned adaptation of the set wiper arm trajectory so that impacts of the wiper arm on the A-columns of the motor vehicle are prevented.
The desired wiping angle varies according to different operating conditions. These variations cause excessive wiping or insufficient wiping coverage of the desired wiped area. A wedge-shaped area on the window between the turning points is sometimes wiped and sometimes not wiped. With long wiper arms it can be especially large and optically troublesome. Furthermore the different sized wiped areas caused by the non-uniform wiping produce a notable operator discomfort during wiping. Finally these wedge-shaped regions must be considered during calculation of tolerances for the wiper field.
Control devices and methods for adaptation of the wiper arm trajectory by the window wiper apparatus are known in the state of the art. These control devices change the set wiper arm trajectory by including information regarding occurring set parameter limits. For example, EP-0700342 B1 discloses a method of this type, in which changes of the set wiper arm trajectories take place with the help of a commercially available control engineering method.
The textbook by Gerd Schulz, xe2x80x9cControl Engineering (Regelungstechnik)xe2x80x9d (Oldenbourg Press (Verlag), Munich, Wein, ISBN 3-486-25858-3) at pages 121 and following, provides examples or illustrations for state estimation by means of a state monitor.
It is an object of the present invention to provide a control method for a window wiper apparatus of the above-described type, which reacts better to changing wiper conditions.
It is another object of the present invention to provide a control device for a window wiper apparatus of the above-described type for performing the control method according to the invention, so that the wiper apparatus reacts better to changing wiper conditions.
The method of the invention controls operation of a wiper device of a window wiper apparatus, especially of a motor vehicle, in which a wiper arm of the wiper device oscillates over a wiping angle defined by two turning points. According to the invention this method comprises adaptation of a set value of the wiping angle to changing operating conditions with the help of a monitoring-assisted process.
The control device for a wiper device of a window wiper apparatus, especially of a motor vehicle, comprises means for controlling cyclic oscillation of at least one wiper arm of the wiper device over a wiping angle defined by two turning points. The control device according to the invention performs the method for adaptation of a set value of the wiping angle to changing operating conditions with the help of a monitoring-assisted process.
Preferred embodiments of the control device and method are described in the following description and claimed in the appended claims.
According to the invention the control device for controlling a wiper device of a window wiper apparatus, especially of a motor vehicle, comprises means for adaptation of a set value of the wiping angle. The adaptation advantageously occurs with the help of a monitoring-assisted process, which establishes the actual current operating point of the wiper arm. In this way both over-wiping and too little wiping of the wiper area can be prevented or at least reduced. The accuracy of the wiping of the wiper arm, especially at the turning points, is advantageously increased.
Advantageously the set value of the wiping angle as well as the course or trajectory of the wiper arm can be sufficiently adjusted to changing wiper conditions on the window. Hardly any-additional sensor technology is required in order to adjust the set value of the wiping angle at the existing operating point. Thus development and manufacturing efforts and costs connected with them are saved. The reproducibility of the wiping angle, especially at the turning points, advantageously increases by adjusting the wiping angle to the actual operating point of the wiper arm.
Even better, the control device according to the invention operates with the appropriate control method during each wiper cycle of the wiper arm, so that an individual wiper cycle defines a complete motion path or course of the wiper arm between two set turning points (upper and lower turning point) on the window.
Preferably the control device according to the invention determines dynamic properties of the window wiper apparatus with the help of a mathematical trajectory model for the wiper arm and stores them. Characteristics of an electric motor, as well as the elasticity and inertia of the window wiper apparatus, are formulated in the trajectory model.
Preferably the usually not measurable load moment on the wiper arm can be included as a perturbation, which acts on the trajectory model, by means of a mathematical model for the perturbation.
The actual load moment on the wiper arm can be determined in preferred embodiments of the method by means of an estimation process with the help of a state monitoring device. Additional state variables for the trajectory model, such as wiper arm acceleration or electric motor current, can be determined by means of additional sensor technology or by filtering already known measured variables.
Thus the operating point, at which the wiper arm actually is, together with the variables determined by the state monitor, the load moment on the wiper arm and the wiper speed (wiping angle rate of change), are sufficiently well known. Moreover with the help of a device for adaptation of a set value of the wiping angle the load moment on the wiper arm is evaluated and a set value of the wiping angle or the set turning points of the wiper arm is or are adapted to the established operating point.
Furthermore in additional preferred embodiments different measurement technology and signal processing signals are used as input variables for the state or condition monitor. Also an input voltage or an input current of the electric motor of the wiper device and a measured output signal of the wiper device, for example a rotation angle after the electric motor or after the gear unit, are numbered among the input variables.